Method and apparatus for polishing with abrasive charged polymer substrates

Method and apparatus for polishing with abrasive charged polymer substrates

An abrasive article for polishing a surface of a workpiece. The abrasive article includes a plurality of polishing islands arranged to interact with a workpiece to maintain a substantially constant contact area. Abrasive features are associated with at least some of the plurality of polishing islands. The abrasive features apply cutting forces to the work piece during motion of the abrasive article relative to the workpiece.Related Terms:Polymer

FIELD OF THE INVENTION

The present disclosure is directed to a method and apparatus for polishing with an abrasive article having a plurality of polishing islands arranged to generate a constant contact area during polishing.

BACKGROUND OF THE INVENTION

Semiconductor wafers are typically fabricated using photolithography, which is adversely affected by inconsistencies or unevenness in the wafer surface. This sensitivity is accentuated with the current drive toward smaller, more highly integrated circuit designs. After each layer of the circuit is etched on the wafer, an oxide layer is put down as the base for the next layer. Each layer of the circuit can create roughness and waviness to the wafer that is preferably removed before depositing the next circuit layer. For many semiconductor applications the chemical mechanical processing (“CMP”) is customized for each layer. A change in a single processing parameter, such as for example, pad design, slurry formulation, or pressure applied by the pad, can require the entire CMP process to be redesigned and recertified.

Magnetic media have similarly stringent planarization requirements as data densities approach 1 Terabyte/inch2 (1 Tbit/in2) and beyond, especially on bit patterned media and discrete track media, such as illustrated in U.S. Pat. Publication 2009/0067082. FIGS. 1 and 2 illustrate the shape of bits formed by etching, such as ion milling or reactive etching. Note that the tops of the bits are rounded, leading to head media spacing loss, roughness at the rounded areas, and magnetic damage due to etching of magnetic materials. Such bits are not viable for magnetic recording. The uneven material increases head media spacing and potential damage to the diamond-like-carbon overcoats. CMP processes have proven inadequate to achieving smooth and flat tops both before and after magnetic material deposition.

CMP is currently the primary approach to planarizing wafers, semiconductors, optical components, magnetic media for hard disk drives, and bit patterned or discrete track media (collectively “substrates”). CMP uses pads to press sub-micron sized particles suspended in the slurry against the surface of the substrate. The nature of the material removal varies with the hardness of the CMP pad. Soft CMP pads conform to the nanotopography and tend to remove material generally uniformly from the entire surface. Hard CMP pads conform less to the nanotopography and therefore remove more material from the peaks or high spots on the surface and less material from low spots.

Traditionally, soft CMP pads have been used to remove a uniform surface layer, such as removing a uniform oxide layer on a semiconductor device. Polishing a substrate with a soft pad also transfers various features from the polishing pad to the substrate. Roughness and waviness is typically caused by uneven pressure applied by the pad during the polishing process. The uneven pressure can be caused by the soft pad topography, the run out of the moving components, or the machined imperfections transferred to the pads. Run-out is the result of larger pressures at the edges of the substrate due to deformation of the soft pad. Soft pad polishing of heterogeneous layered materials, such as semiconductor devices, causes differential removal and damage to the electrical devices.

A CMP pad is generally of a polyurethane or other flexible organic polymer. The particular characteristics of the CMP pad such as hardness, porosity, and rigidity, must be taken into account when developing a particular CMP process for processing of a particular substrate. Unfortunately, wear, hardness, uneven distribution of abrasive particles, and other characteristics of the CMP pad may change over the course of a given CMP process. This is due in part to water absorption as the CMP pad takes up some of the aqueous slurry when encountered at the wafer surface during CMP. This sponge-like behavior of the CMP pad leads to alteration of CMP pad characteristics, notably at the surface of the CMP pad. Debris coming from the substrate and abrasive particles can also accumulate in the pad surface. This accumulation causes a “glazing” or hardening of the top of the pad, thus making the pad less able to hold the abrasive particles of the slurry and decreasing the pad's overall polishing performance. Further, with many pads the pores used to hold the slurry become clogged, and the overall asperity of the pad's polishing surface becomes depressed and matted.

Shortcomings of current CMP processes affect other aspects of substrate processing as well. The sub-micron particles used in CMP tend to agglomerate and strongly adhere to each other and to the substrate, resulting in nano-scale surface defects. Van der Waals forces create a very strong bond between these surface debris and the substrate. Once surface debris form on a substrate it is very difficult to effectively remove them using conventional cleaning methods. Various methods are known in the art for removing surface debris from substrates after CMP, such as disclosed in U.S. Pat. Nos. 4,980,536; 5,099,557; 5,024,968; 6,805,137 (Bailey); 5,849,135 (Selwyn); 7,469,443 (Liou); 6,092,253 (Moinpour et al.); 6,334,229 (Moinpour et al.); 6,875,086 (Golzarian et al.); 7,185,384 (Sun et al.); and U.S. Patent Publication Nos. 2004/0040575 (Tregub et al.); and 2005/0287032 (Tregub et al.), all of which are incorporated by reference, but have proven inadequate for the next generation semiconductors and magnetic media.

Current processing of substrates for semiconductor devices and magnetic media treats uniform surface layer reduction, planarization to remove waviness, and cleaning as three separate disciplines. The incremental improvements in each of these disciplines have not kept pace with the shrinking feature size of features demanded by the electronics industry.

BRIEF

SUMMARY

The present disclosure is directed to an abrasive article for polishing a surface of a workpiece. The abrasive article includes a plurality of polishing islands arranged to interact with a workpiece to maintain a substantially constant contact area. Abrasive features are associated with at least some of the plurality of polishing islands. The abrasive features apply cutting forces to the work piece during motion of the abrasive article relative to the workpiece.

The plurality of polishing islands can form a curvilinear repeating and staggered arrangement for rotary polishing operations. Alternatively, the plurality of polishing islands form a repeating and staggered island pattern for linear operations. In another embodiment, the plurality of polishing islands are arranged in a curvilinear form along the center of rotation of a circular or rotating polishing pad. The plurality of polishing islands are optionally pads arranged at an oblique angle with respect to the workpiece.

The present disclosure is also directed to an abrasive article for polishing a workpiece including a plurality of polishing islands arranged to intersect with a workpiece to maintain a substantially constant contact area. At least some of the polishing islands include a first surface engaged with the workpiece, and a second surface, attached to a polyamide substrate. The plurality of polishing islands are arranged in a cascade arrangement so as to cause a substantially invariant hydrodynamic film under the workpiece during motion of the abrasive article relative to the workpiece.

The first surface optionally includes an abrasive features including one or more of a nano-scale roughened surface coated with a hard coat, nano-scale diamonds attached to a trailing edge of the first surface, an abrasive particles attached to a film, or an abrasive composite. The polishing pads optionally include abrasive portions having a plurality of different lengths as measured along a direction of motion of the abrasive article relative to the substrate.

The present disclosure is also directed to an abrasive article for polishing a workpiece including a first polishing island, a second polishing island, and a non-straight link connecting the first polishing island and the second polishing island. The polyimide material is optionally coupled to the first polishing island and the second polishing island. In one embodiment, a sponge like pad is coupled to the first polishing island and the second polishing island. A preload is placed onto the workpiece via a sponge like pad.

The present disclosure is also directed to an abrasive article for polishing a surface of a workpiece including a plurality of polishing islands arranged to intersect with a workpiece to maintain a substantially constant contact area. At least some of the plurality of polishing islands are connected to other polishing islands with a non-straight link. The polishing substrate contains abrasive features applying cutting forces to the work piece during motion of the abrasive article relative to the slider bar.

The present disclosure is directed to an abrasive article for polishing a substrate surface. The abrasive article includes a holder pad assembly and an abrasive member held in place with respect to a holder pad. The abrasive member further includes a first surface engaged with the holder pad assembly, and a second surface including an abrasive. A preload mechanism is positioned to bias the second surfaces of the abrasive member toward the substrate surface. One or more fluid bearing features on the second surface of the abrasive member are configured to generate lift forces during relative motion between the abrasive article and the substrate surface.

In one embodiment, at least one abrasive feature is located on the second surface of the abrasive member. The abrasive feature applies a cutting force to the substrate surface during relative motion between the abrasive article and the substrate surface. The fluid bearing can be hydrostatic or hydrodynamic. The abrasive feature can be diamond like carbon or aluminum oxide. The abrasive feature can be a shaped abrasive feature.

The abrasive article is optionally suspended with a gimballing mechanism or a hydrostatic preload.

In one embodiment, abrasive features are located at an interface of the abrasive article and the substrate. The abrasive features polishing the substrate during motion of the polishing article relative to the substrate. The abrasive features can be one or more of an abrasive material attached to the polishing pads, a slurry of free abrasive particles located at the interface with the substrate, or a combination thereof. The polishing islands are preferably arranged in a circular array, a rectangular array, an off-set pattern, or a random pattern.

The polishing islands optionally include one or more fluid bearing features configured to generate lift forces during motion of the polishing article relative to the substrate. The fluid bearing features are optionally abrasive composites. The lift force is one of aerodynamic lift or hydrodynamic lift.

The polishing pads can be configured to be one of topography following or topography removing. The polishing article optionally includes at least one sensor. The preload flexures are optionally springs.

The present application is also directed to an abrasive article with an array of independently gimballed abrasive members that are capable of selectively engaging with nanometer-scale and/or micrometer-scale height variations and micrometer-scale and/or millimeter-scale wavelengths of waviness, on the surfaces of substrates. The gimbals permit each abrasive member to move independently in at least pitch and roll relative to the substrate. The present abrasive article can be used before or after features are formed on the substrates.

In one embodiment, each abrasive member maintains a fluid bearing (air is the typical fluid) with the substrate. The spacing, which includes clearance, pitch, and roll, of the abrasive members can be adjusted to follow the topography of the substrate to remove a generally uniform layer of material; to engage with the peaks on the substrate to remove target wavelengths of waviness; and/or to remove debris and contamination from the surface of the substrate.

A hydrodynamic and/or hydrostatic bearing is used to provide vertical, pitch and roll stiffness to the abrasive member and to control the spacing and pressure distribution across the fluid bearing features on the abrasive members. Adjustments to certain variables, such as for example, the spacing (which includes minimal spacing and attitude of the abrasive members), pitch and roll stiffness which control attitude, the preload, and/or the abrasive features can be used to modify the cutting force applied to the substrate

Fluid bearing structures are fairly complex with a substantial number of variables involved in their design. The primary forces involved in a given fluid bearing are the gimbal structure and the preload. The gimbal structure applies both a pitch and roll moments to the individual abrasive members, and hence, the fluid bearing structures. If the gimbal is extremely stiff, the fluid bearing may not be able to form a pitch or roll angle. The preload and preload offset (location where the preload is applied) bias the fluid bearing toward the substrate. The preload is typically applied by a different structure than the gimbal structure.

Fluid bearing surface geometry plays a large role in pressurization of the bearing. Possible geometries include tapers, steps, trenches, crown, cross curves, twists, wall profile, and cavities. Finally, external factors such as viscosity of the bearing fluid and linear velocity play an extremely important role in pressurizing bearing structures.

The individual abrasive members are capable of selectively engaging with nanometer-scale and micrometer-scale height variations and/or micrometer-scale or millimeter-scale wavelengths of waviness on the surface of substrates to perform one or more of the following three overlapping and complementary functions: 1) following the topography of the substrate to remove a generally uniform layer of material; 2) engaging with the peaks on the substrate to remove target wavelengths of waviness; and/or 3) removing debris and contamination from the surface of the substrate. Consequently, the present abrasive articles can be engineered to perform a wide variety of functions, including lapping, planarization, polishing, cleaning, and burnishing substrates.

In connection with performing any of these three functions, the abrasive members may 1) include abrasive features positioned to interact with the substrate, 2) interact with free abrasive particles at the interface with the substrate, or 3) a combination thereof. Free abrasive particles can be used with either topography following or topography removing abrasive members.

While the abrasive features generally have a hardness greater than the substrate, this property is not required for every embodiment since any two solid materials that repeatedly rub against each other will tend to wear each other away. For example, relatively soft polymeric abrasive features molded on the abrasive members can be used to remove surface contaminants or can interact with free abrasive particles to remove material from the surface of a harder substrate. As used herein, “abrasive feature” refers to a portion of an abrasive member that comes in physical contact with a substrate or a contaminant on a substrate, independent of the relative hardness of the respective materials and the resulting cut rate.

FIG. 3A is a schematic illustration of a topography following abrasive member 1000 in accordance with an embodiment of the present invention. The abrasive member 1000 is typically designed to follow the topography by assuring that the trailing edge area has the largest pressure peak. For example, the fluid bearing can be pitched to ensure that the leading edge is spaced substantially higher above the substrate than the trailing edge. The trailing edge 1006 of the abrasive member 1000 applies a cutting force to nanometer-scale and/or micron-scale height variations 1008 on the surface 1004, while following the millimeter-scale and/or micrometer-scale wavelengths in the waviness 1010 on the substrate. Consequently, the abrasive member 1000 removes a generally uniform layer of material 1012 from peaks 1014 as well as valleys 1016 on the surface 1004, such as for example, removing or controlling the thickness of an oxide layer. As used herein, “topography following” refers to an individually gimbaled abrasive member that generally follows millimeter-scale and/or micrometer-scale wavelengths of waviness on a substrate, while engaging with nanometer-scale height variations to primarily remove a generally uniform amount of material from the surface.

FIG. 3B is a schematic illustration of a topography removing abrasive member 1050 in accordance with an embodiment of the present invention. The leading edge 1056 and/or trailing edge 1058 of the abrasive member 1050 applies a cutting force to peaks 1060 of millimeter-scale and/or micrometer-scale wavelengths of the waviness 1062 on the surface 1054 of the substrate, with minimal engagement with the valleys 1064. Consequently, the abrasive member 1050 removes more material from the peaks 1060 than the valleys 1064. As used herein, “topography removing” refers to an individually gimbaled abrasive member that primarily removes nanometer-scale and/or micrometer-scale height variations from peaks of millimeter-scale and/or micrometer-scale wavelengths in the waviness on a substrate.

FIG. 3C is a schematic illustration of a cleaning abrasive member 1100 in accordance with an embodiment of the present invention. The leading edge 1114 and/or the trailing edge 1106 of the abrasive member 1100 follows the millimeter-scale and/or micrometer-scale wavelengths in the waviness 1108 on the substrate, while applying a cutting force to nanometer-scale and/or micron-scale contaminants 1110. The abrasive member 1100 preferably has a spacing 1112 such that little or no material is removed from the surface 1104 of the substrate other than the contaminants 1110. As used herein, “cleaning” refers to an individually gimbaled abrasive member that generally follows millimeter-scale and/or micrometer-scale wavelengths in the waviness of a substrate, while primarily engaging with nanometer-scale and/or micrometer-scale height contaminant on the surface, with little or no material removal from the surface.

Since the abrasive members engage with nanometer-scale and micrometer-scale structures, it is unlikely that any particular embodiment will perform one of the topography following, topography removing, or cleaning functions to the exclusion of the other two. Rather, the present application adopts a probabilistic approach that a particular embodiment is more likely to perform one function, recognizing that the other two functions are also likely being performed in varying degrees.

For example, the topography following abrasive member 1000 of FIG. 3A can also remove some or all of the surface contaminants 1110 of FIG. 3C. In another example, the pressure applied to peaks 1014 in FIG. 3A may be greater than in the valleys 1016, resulting in more material removal from the peaks 1014, such as illustrated in FIG. 3B. The topography removing abrasive member 1050 may engage sidewalls 1066 of the peaks 1060 or the valley 1064, such as illustrated in FIG. 3A. The cleaning abrasive member 1100 may contact the surface 1104 and remove a generally uniform layer of material from the substrate, along with the contaminants 1110. Therefore, the definitions of “topography following”, “topography removing”, and “cleaning” should not be read as mutually exclusive. It should be assumed that the design parameters of the abrasive members can be modified to emphasize more of one function than the others.

Various abrasive features are available for the present abrasive members, such as for example, a surface roughness formed on the leading and/or trailing edges of the abrasive members. That surface roughness may include a hard coat, such as for example, diamond-like-carbon. In another embodiment, the abrasive features may be discrete abrasive particles, such as for example, fixed diamonds. In yet another embodiment, the abrasive features may be structured abrasives, discussed further below.

For example, to remove all the wavelengths smaller than a desired value, the dimensions of the abrasive members can be greater than the target wavelengths. The wavelengths are determined by the gas pressure profile generated by the abrasive member and the size of the abrasive member. As a rule of thumb, the smallest circumferential wavelength is about one-fourth the length of the abrasive members.

The dimensions of the abrasive members and the pressure profile due to the hydrostatic and/or hydrodynamic lift (gas and/or liquid) determine the ability of the abrasive member to follow the waviness of the substrate. Assuming that the abrasive members can follow ¼ of its size, then all wavelengths smaller than the ¼ will cause interference with the abrasive members and material removal will ensue due to the interactions. Portions of the abrasive members generate a hydrodynamic lift causing predictable waviness following capability and stabilizing force countering the cutting forces.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is the configuration of a single bit on a bit patterned media for a hard disk drive.

FIG. 2 is a perspective view of an array of bits on a bit patterned media.

FIG. 3A is a schematic illustration of a topography following abrasive member in accordance with an embodiment of the present disclosure.

FIG. 3B is a schematic illustration of a topography removing abrasive member in accordance with an embodiment of the present disclosure.

FIG. 3C is a schematic illustration of a cleaning abrasive member in accordance with an embodiment of the present disclosure.

FIG. 4 is a schematic illustration of an idealized bit for bit patterned media in accordance with an embodiment of the present disclosure.

FIG. 5 is an exploded view of an abrasive article with gimbaled abrasive members in accordance with an embodiment of the present disclosure.

FIG. 6 is a perspective view of a preload mechanism for the abrasive article of FIG. 5.

FIG. 7 is a perspective view of a gimbal structure for the abrasive article of FIG. 5.

FIG. 8 is a detailed perspective view of a gimbal structure for the abrasive article of FIG. 5.

FIG. 9 is a perspective view of the abrasive members for the abrasive article of FIG. 5.

FIG. 10 is another perspective view of the abrasive members for the abrasive article of FIG. 5.

FIG. 11 is a perspective view of the abrasive article of FIG. 5 polishing a substrate in accordance with an embodiment of the present disclosure.

FIG. 12 is a perspective view of the fluid bearing surface on the abrasive members of FIG. 5.

FIG. 13 is a detailed perspective view of the fluid bearing surface on the abrasive members of FIG. 5.

FIG. 14 is a conceptual view of an abrasive member interacting with a substrate in a topography following mode in accordance with an embodiment of the present disclosure.

FIG. 15 is a conceptual view of an abrasive member interacting with a substrate in a topography removing mode in accordance with an embodiment of the present disclosure.

FIG. 16 is a conceptual drawing of a roughened abrasive surface in accordance with an embodiment of the present disclosure.

FIG. 17 is a side sectional view of an abrasive surface with nano-scale diamonds attached to a polymeric backing in accordance with an embodiment of the present disclosure.

FIGS. 18A and 18B are conceptual illustrations of a structured abrasive surface in accordance with an embodiment of the present disclosure.

FIG. 19 is a perspective view of a unitary abrasive article in accordance with an embodiment of the present disclosure.

FIG. 20 is a perspective view of the gimbal assemblies of the abrasive article of FIG. 19.

FIG. 21 is a perspective view of the fluid bearing surfaces of the abrasive article of FIG. 19.

FIG. 22 is an exploded view of an abrasive article with an integral hydrostatic bearing structure in accordance with an embodiment of the present disclosure.

FIG. 23 is a top view of the abrasive article of FIG. 22 with the membrane removed.

FIG. 24 is a detailed top view of the abrasive article of FIG. 22 with the membrane removed.

FIG. 26 is a perspective view of an alternate abrasive article with fluid bearing surfaces that comprise abrasive composites in accordance with an embodiment of the present disclosure.

FIGS. 27A and 27B are side schematic illustrations of abrasive members with various abrasive composite structures at the fluid bearing surfaces in accordance with an embodiment of the present disclosure.

FIGS. 28 and 29 illustrate an alternate abrasive article with grooved fluid bearing surface in accordance with an embodiment of the present disclosure.

FIGS. 30A and 30B are schematic illustrations of double sided substrate processing using an abrasive article in accordance with an embodiment of the present disclosure.

FIG. 31 is a perspective view of a hydrostatic abrasive member assembly in accordance with an embodiment of the present disclosure.

FIG. 32 is a bottom perspective view of an abrasive member in accordance with an embodiment of the present disclosure.

FIG. 33 is a bottom perspective view of the abrasive member of FIG. 32.

FIG. 34 is a bottom perspective view of a gimbal mechanism in accordance with an embodiment of the present disclosure.

FIG. 35 is an exploded view of the hydrostatic abrasive member assembly of FIG. 31.

FIGS. 36 and 37 are perspective views of the hydrostatic abrasive member assembly of FIG. 31.

FIG. 38 is a bottom perspective view of the hydrostatic abrasive member assembly of FIG. 31.

FIG. 39A is a perspective view of an annular fluid bearing surface in accordance with an embodiment of the present disclosure.

FIG. 39B is a pressure profile graph of the fluid bearing of FIG. 39A.

FIG. 40 is a perspective view of a hydrodynamic abrasive member in accordance with an embodiment of the present disclosure.

FIG. 41 is a pressure profile graph for the abrasive member of FIG. 40.

FIG. 42 is an exploded view of a hydrodynamic abrasive member assembly in accordance with an embodiment of the present disclosure.

FIG. 43 is a perspective view of the hydrodynamic abrasive member assembly of FIG. 42.

FIGS. 44A-44C are various views of a cylindrical array of abrasive members in accordance with an embodiment of the present disclosure.

FIG. 45 is an exploded view of the cylindrical array of abrasive members of FIGS. 44A-44C.

FIG. 46 is a plurality of the cylindrical array abrasive member assemblies of FIGS. 44A-44C in accordance with an embodiment of the present disclosure.

FIG. 47A is a schematic illustration of an abrasive member for topography following applications in accordance with an embodiment of the present disclosure.

FIG. 47B is a pressure profile for the abrasive member of FIG. 47A.

FIG. 48A is a schematic illustration of an abrasive member for topography following applications in accordance with an embodiment of the present disclosure.

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